1. Field of the Invention
The present invention relates to a liquid crystal display device and a manufacturing method thereof.
2. Description of the Related Art
An example of a basic constitution of a liquid crystal display device which uses thin film transistors (also referred to as “TFTs” in this specification) as driving elements is constituted as follows. TFTs, scanning lines or signal lines are formed on a first transparent substrate, color filters are formed on a second transparent substrate, and liquid crystal is inserted into a gap between the first and second transparent substrates while arranging a TFT forming surface or a color filter forming surface at the inside of the respective substrates. The TFTs on the first substrate are arranged on respective pixel regions. Further, with respect to color filters on the second substrate, color regions consisting of red (R), green (G), blue (B) are arranged in a stripe shape and a black matrix constitution made of metal is adopted as partitions for color filters (also referred to as “CFs” in this specification) of respective colors CF. The brightness, that is, the numerical aperture of the liquid crystal display device having such a constitution is largely reduced when the positioning accuracy of the first and second substrates is poor and this adverse influence is worse than the positioning accuracy among the TFTs, the scanning lines and the signal lines on the first substrate. Accordingly, there has been publicly proposed a technique which is generally called “a color-filter on TFTs”. This technique is characterized by simultaneously forming color filters and a black matrix which have been formed on the second substrate conventionally along with the formation of the TFTs, the scanning lines, the signal lines or the like on the first substrate.
On the other hand, as a system which broadens a viewing angle of the liquid crystal display device, there have been proposed an IPS (In-Plane-Switching) type and a FSS (Fringe-Field-Switching) type. In the IPS type, by rotating liquid crystal molecules substantially horizontally with respect to substrates, pixel electrodes and common electrodes for driving liquid crystal are simultaneously formed on the first substrate and an electric field is generated substantially horizontally with respect to the substrates by applying a voltage between two electrodes. In the FSS type, either one of the pixel electrodes and the common electrodes are formed in a planar shape without forming them in a comb-like shape and comb-like electrodes are formed on the electrodes by way of an insulation film. The FSS type is disclosed in Japanese Laid-open Patent Publication 202356/1999.
Further, a method which realizes a color filter/on/TFT using the IPS type is disclosed in Japanese Laid-open Patent Publication 111957/2000.